The invention relates to scintillators, and more particularly relates to scintillation cameras which produce images of a patient under investigation. In its most advantageous application, the invention relates to scintillation cameras which produce tomographic images.
In imaging applications, a scintillation flash is associated with an X-Y position (referenced to the plane of the sensitive surface of the scintillator). However, a scintillator is not infinitesimally thin, and as a result, the apparent X-Y location of a scintillation flash may be, and usually is, different from the location of the scintillation event which generated the flash. Accordingly, to precisely locate the situs (and thus the true X-Y position) of a scintillation event, both the apparent X-Y position of the resulting flash and the depth of the event within the scintillator must be known.
While the photodetectors which detect scintillation flashes are set up to register the apparent X-Y position of a scintillation flash, no method is known by which a single photodetector can be used to determine the depth of a scintillation event within the scintillator. The inability to determine this depth places a limitation on the precision with which a scintillation event can be localized within the X-Y plane. This in turn limits the spatial resolution of images produced by the imaging camera.
Even where X-Y position information is unimportant, such as in oil well logging, it is still useful to determine the depth of a scintillation event within a scintillator. This is because the output of light from a scintillator is a function of the depth of the scintillation event within the scintillator. The energy of incident radiation affects the intensity of a scintillation flash and this energy can be better estimated by correcting for the depth dependence of light output from the scintillator. Consequently, energy resolution can be improved if the depth of a scintillation event within a scintillator is known. The improvement can be significant in, e.g., scintillators which are used in oil-well logging, because such scintillators are usually very thick.
It would therefore be advantageous to determine the depth at which incoming radiation interacts with a scintillator to produce a scintillation event.
One object of the invention is to provide a scintillator system which is so designed that the depth of a scintillation event within the scintillator can be determined.
A further object is to provide a scintillation camera system which utilizes the depth so determined in production of a planar or tomographic image.
Another object is, in general, to improve on known devices and techniques.